The Security Intelligence Service declined to release confidential documents at the centre of "dirty politics" allegations to reporters - but passed the briefing notes to blogger Cameron Slater.

Investigative journalist Nicky Hager's new book contains allegations that Slater was tipped off by Prime Minister John Key's staff to ask for the papers.

The documents embarrassed former Labour leader Phil Goff by showing he was briefed by the spy agency in 2011 about alleged Israeli activity in Christchurch.

Hager suggests Key's office ensured Slater got the briefing notes, which he used as a basis for an article on his Whaleoil blog, accusing Goff of lying. Key is the minister responsible for the SIS.

About the same time, The Dominion Post's request for the documents was declined.

In Dirty Politics, published this week, Hager says Slater received a response to his Official Information Act request within a week - and quotes Facebook messages which suggest Slater knew what to expect.

The documents were stamped as being declassified on July 26, the same day Slater lodged his request, Hager notes.

The Whaleoil post attacking Goff appeared on August 4. On the same day The Dominion Post contacted Key's office to inquire why its request for the documents had been refused within two days.

The SIS explained away the different treatment by arguing that The Dominion Post also sought a copy of the briefing notes supplied to Key. However, this was the same document given to Goff.

In response to questions, a spokesman for Key insisted that "at no stage did [his office] direct how the NZ SIS should treat the OIA request".

Fallout from Hager's book continued yesterday, with the author saying he might release Slater's emails to back up his claims.

Key said the claims were "dissolving" and has vowed not to take any action against Justice Minister Judith Collins, who is alleged to have leaked sensitive information to Slater.

The theme of Hager's book is that National used Right-wing blogs to smear its opponents.

Slater says his emails were hacked and the contents misconstrued.

Pollster and blogger David Farrar said yesterday he believed documents were stolen from his offices by an employee.

He intended to lay a complaint with police and said the breach of his privacy had him considering stepping back from politics.

Collins has also "utterly" rejected most of the claims levelled at her.

But she admitted passing on a public servant's name who Slater then alleged was leaking information to Labour.